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Topic: Latest PIOMAS update (August) (Read 565441 times)

The gridded thickness animation of May 2017. The situation in the Fram is crazy.

And note the 4m stretch to the north of Greenland. Near the end of the animation you can see it start to disappear as it prepares to be flushed down Nares.

Apart from these two critical locations, overall distribution of thickness became even worse during May. Near-term there may be some respite in Fram and Nares export, but the weakening in the central pack is likely to ramify for the rest of the melt season.

....Initially, Arctic amplification (resulting in late season open water with high absorbance) is a poor match with the timing of solar energy peak input, but the overlap will improve in coming years. However open water in Sep-Oct-Nov is already important to irrevocable de-stratification and heat transfer from ocean to atmosphere. ....

While the "blue water" advance toward higher-insolation season might be slow, there has already been a rapid - if inconsistent - increase in the amount of first-year ice susceptible to melt ponding. Its effect is harder to gauge, of course, because of interaction with weather conditions.

How did you post a june average monthly value today? is that a projection?why is the june average monthly value (around 8,000 km^3 so much less than the daily sine-wave ice volume graph for june 1st which is closer to 18,000 km^3?

Do you perchance have pixel counts for your 16 thickness bins? If those numbers were available for each member of a time series, it would be neat to make one of those wiggle line graphics (area ordinate, thickness abcissa) to see how the proportioning of volume across thickness classes is changing. This assumes that the Piomas grid is more or less equal-area. This would be similar but different from how NSIDC does their ice age classes (as a normalized stack).

It may be that daily numbers are too noisy and some sort of rolling or weekly average would be necessary. It might be best just to address the Arctic Ocean basin.

The graphic below just shows pixel counts for each bin for a single day (31 May 17) when the ice was predominantly 1.5 to 2.0 m thick. The inset, which is to the same scale and orientation, shows hycom-envisioned thickness exported out the Fram and Nares from May 1st to June 9th.

During May, Arctic sea ice volume began to decline from its annual maximum for 2017. The volume maximum occurs one month later than the extent maximum because some areas continue to thicken while the extent begins to recede. Arctic sea ice volume through May 2017 continued substantially below prior years. May 2017 sea ice volume was 19,800 km3 , 1200 km3 below the previous record from May in 2016. The low sea ice volume results of anomalously high temperatures throughout the Arctic for November through January discussed here and here. May volume was 39% below the maximum May ice volume in 1979, 27% below the 1979-2016 mean, and more than 1.3 standard deviations below the long term trend line.

Hence, if the storms that drive dispersion and export of our highly mobile pack continue, then the amount of in situ melting, do to warm weather & insolation, will matter less relative to volume.

That's not to say that above normal warming & insolation won't significantly compound the nonlinear rate of loss, it's just not necessary like 2012. Now we need both below normal temps, clouds and minimal winds to avoid record losses of sea ice volume, area and extent.

The significance for me of the May PIOMAS volume is that it is 1200 km3 below the 2016 may volume, which itself was a record low, and that 1200 km3 represents about 4 years of average May annual volume loss. And then I looked at that scary average thickness graph and gulped.

(April's decline was larger, but was with 2011. It was my layman's view that this simply put volume reduction back to the average annual loss of maximum volume of about 300 km3.)

Arithmetic says volume reduction cannot proceed at an annual percentage so much greater than extent loss indefinitely. But that speculation belongs elsewhere.

Something's not adding up. Over at Juan's When will be break PIOMAS 2012 September record? thread, he shows the May 2016 average was 21.03 thousand km3, which is ~2200 km3 more than 18.8, not 1200. Is that number wrong, or am I comparing the wrong things?

You are right. They haven't published the exact figure, but 21.026 - 18.800 (rounded) = 2,226 km3.

Fill the second questionnaire to have the official numbers. I just copy/paste, with some formating.

They are still of course in error, as it is 19.8 km3 and obviously not 19,800 km3...

When quoted as 19.8 the units are k Km3 ie thousand km3 So they are correct in saying 19,800 km3 (with , as separator not decimal point).

Oh dear. Of course you are right... in the files it's in 1000s of km3. Stupid mistake of mine.

this what you say and in addition it's good to be aware that in some countries one is using a "," to separate dezimals and in other countries they are using a "." to do the same, so 19,800 in the Spain and other countries would be the same like 19.800 in switzerland and other countries for example.

What I find most noteworthy is that most of the anomalously thick ice finds itself in an area where ice export is strong and there is little chance that any of this thick ice will survive the summer.

And yet, most of the thickest ice is still hanging out along the CAA. It's just not as thick as it used to be and far more mobile. It will be the last area in the Arctic where sea ice hangs on at the end of the melt season.

I am afraid that even all of it is made up of poorly bonded smaller floes, and will flush way when the real heat gets there. Open water in that area is heating up by the day, along with the breeze that's already above zero.

I am afraid that even all of it is made up of poorly bonded smaller floes, and will flush way when the real heat gets there. Open water in that area is heating up by the day, along with the breeze that's already above zero.

The "Garlic Press" last year does suggest the the Nares has been joined by other channels in the CAA in draining the thickest ice south.

most of the thickest ice is along the CAA [Shared]inquired at APL UW about Piomas blob anomaly [Neven]

The animation below traces the history of the peculiarly thick ice from June 2016 (using Zack's monthly) to 31 May 2017 (using every 5th day of wip's daily animations for 2017, earlier were not available as Greenland down, polar stereographic).

The inset shows ice motion for the same days. Whatever the merits of hycom thickness, it does show ice pack motion effectively and accurately, per Sentinel S-1 imagery mosaics at DTU.

In addition to a long period during which the thickest ice was not along the CAA as expected, it appears that the Piomas thickness anomaly is not quite moving along with the ice pack. Hopefully there was a response to Neven's inquiry.

I've added a 2016 capture from the remarkable 1990 - Nov 2016 NSIDC Tshudi sea ice age video. The full length, full size movie is here: https://youtu.be/c6jX9URzZWg?t=20. Again, there is nothing corresponding to the Piomas blob; the oldest ice (often the thickest) is mosltly found along the CAA but also gyres around to the west, alternating with periodic pulses out the Fram.

The third images drapes the thickness color classes over a 3D aerial view using grayscale height. (The palette steps Wipneus uses in these admirable maps are not quite uniform, upper left staircase.)

....In addition to a long period during which the thickest ice was not along the CAA as expected, it appears that the Piomas thickness anomaly is not quite moving along with the ice pack. Hopefully there was a response to Neven's inquiry.

I've added a 2016 capture from the remarkable 1990 - Nov 2016 NSIDC Tshudi sea ice age video. The full length, full size movie is here: https://youtu.be/c6jX9URzZWg?t=20. Again, there is nothing corresponding to the Piomas blob; the oldest ice (often the thickest) is mosltly found along the CAA but also gyres around to the west, alternating with periodic pulses out the Fram.

Have a look at the "Fram strait thread" where I have posted animations of movements into Fram strait based on some of your earlier suggestions. Piomas shows thickening by compaction for example along the north coast of the Svalbard islands (I am not convinced that this is as strong as PIOMAS makes it in light of the bottom melt I would expect at the western end of that area)

I have posted animations of movements into Fram ... Piomas shows thickening by compaction up against Svalbard islands ... not convinced that this is so strong

Yes, the corralled ice animations have been excellent.

It "makes sense" to have the model pile up ice against Svalbard given strong and persistent winds pushing the whole pack that way, adding to Transpolar Drift. Hycom shows that too in 2017 from about day 78 on but predicts considerable dissipation by 11 June. Franz Joseph Land is less affected, as expected from surface currents.

Such a dramatic event should leave its mark on Sentinel 2AB imagery (offered at the EOS playground site) as this has the resolution to show overriding floes (below, no longer visible early June). Sentinel 1AB, which is not clear-day dependent, also has little residual drama as of today.

So while no one here would be surprised to see a thousand km swath open north of Svalbard, FJL, Severnaya Zemlya and beyond later on in June, warm Atlantic waters, Barents and Arctic Ocean currents, shelf bathymetry, warm air, winds and ice dispersion all contribute to attribution.

So as I share the same sentiment, I decided to get out of my shell and actually write an email to Dr. Zhang. I explained briefly how PIOMAS is very popular, as it gives insight that extent doesn't provide, and very politely requested if at all possible to provide mid-month updates of the daily values, in addition to the monthly releases. And today I was very happy to receive a nice response from him. He said sure, he will try to have a mid-month update (it's not guaranteed of course). He added that the updated files would include those daily files: hiday.H, aiday.H, uiday.H, and snowday.H. This means nothing to me, as my to-do task of cracking the PIOMAS files has stalled for now, but I am sure it's all clear to the amazing Wipneus.So hopefully, my PIOMAS addiction will get fed some more in the coming months.

He added that the updated files would include those daily files: hiday.H, aiday.H, uiday.H, and snowday.H. This means nothing to me, as my to-do task of cracking the PIOMAS files has stalled for now, but I am sure it's all clear to the amazing Wipneus.So hopefully, my PIOMAS addiction will get fed some more in the coming months.

Attached two Fram volume export graphs (calculated from PIOMAS ice thickness and velocity). As the monthly graph shows, that transport volume in April was near normal, in May moved to second highest after 2012 (declining considerable less than the "normal").

The daily graph shows that the high transport was still high in the last part of the month.

So I made a "prediction" of sorts for mid-June using the crude indicator of DMI temps. I noticed that 2012 had a unique spike to 0oC about 10 days earlier that other years, more or less on day 150. DMI animation follows.This may have contributed to its unique PIOMAS drop over the days 151-166. The years 2010, 2011 and 2016 all cluster at 2.72-2.84 while 2012 dropped 3.59 (1000 km3).As 2017 appears to follow the more usual DMI trajectory, I can extrapolate 2017 to mid-June at 15.34 (lonely black dot). Chart follows.If this happens 2017 should still lead but by a much smaller lead, ~700 km3.

Oren, all the years in the chart have an accelerated drop in June due to the beginning of summer, though not that strong as it was in the case of 2012. When I look at your dot I feel you ignored this a bit. If you take the average acceleration of each year on the graph (excepting 2012), I would expect to see that black dot closer to 15 million km3.

Oren, all the years in the chart have an accelerated drop in June due to the beginning of summer, though not that strong as it was in the case of 2012. When I look at your dot I feel you ignored this a bit. If you take the average acceleration of each year on the graph (excepting 2012), I would expect to see that black dot closer to 15 million km3.

To clarify - I did take the average drop (during the first half of June) of each year in the graph excepting 2012, used that and got a result of 15.34 (1000 km3).I will be surprised if the actual result exceeds 15.34. I feel it should be a bit below because of the state of the ice and the location distribution of the volume, but I didn't take that into account.

Oren, all the years in the chart have an accelerated drop in June due to the beginning of summer, though not that strong as it was in the case of 2012. When I look at your dot I feel you ignored this a bit. If you take the average acceleration of each year on the graph (excepting 2012), I would expect to see that black dot closer to 15 million km3.

To clarify - I did take the average drop (during the first half of June) of each year in the graph excepting 2012, used that and got a result of 15.34 (1000 km3).I will be surprised if the actual result exceeds 15.34. I feel it should be a bit below because of the state of the ice and the location distribution of the volume, but I didn't take that into account.

my expectation are quite a bit (a lot) lower but interesting to learn from reality and which approach will prevail :-) mid june is not far out by now which makes it a bit difficult but i expect a 2012 like rate of decent withing the next 3 weeks and that would take it beyond the mid june point.

thanks a lot for the input however, very interesting IMO

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Probably doesn't make sense to just be looking at DMI 80N temperatures though, since it only covers about half the basin and completely ignores insolation; I don't necessarily know if it's a good proxy, alone, for estimating volume loss.

Probably doesn't make sense to just be looking at DMI 80N temperatures though, since it only covers about half the basin and completely ignores insolation; I don't necessarily know if it's a good proxy, alone, for estimating volume loss.

thanks for adding this, it is about the line i'm thinking along, just don't have enough insight to interpret the various sources but something appears a bit off and what you say makes sense,at least the doubts are legit.

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Probably doesn't make sense to just be looking at DMI 80N temperatures though, since it only covers about half the basin and completely ignores insolation; I don't necessarily know if it's a good proxy, alone, for estimating volume loss.

Do you perchance have pixel counts for your 16 thickness bins? If those numbers were available for each member of a time series, it would be neat to make one of those wiggle line graphics (area ordinate, thickness abcissa) to see how the proportioning of volume across thickness classes is changing. This assumes that the Piomas grid is more or less equal-area. This would be similar but different from how NSIDC does their ice age classes (as a normalized stack).

It may be that daily numbers are too noisy and some sort of rolling or weekly average would be necessary. It might be best just to address the Arctic Ocean basin.

I did not have such data readily available, also the PIOMAS grid is far from equal area. On the other hand I know the area of each grid cell.

Anyway with the data that I have I may be able to do something of interest. The PIOMAS algorithm calculates at every time-step a thickness distribution for each grid cell. The data is available as gice. Gice gives 12 sub grid cell thickness "bins":[0.00, 0.26, 0.71, 1.46, 2.61, 4.23, 6.39, 9.10, 12.39, 16.24, 20.62, 25.49]The lowest bin is the fraction with "no ice", second bin is the fraction with thickness 0<h<=0.26m and so fort.

So to calculate the area of all ice belonging to a particular bin, I take each cell, multiply the gice[bin] with the cell's area and sum it over the PIOMAS domain.

In the attach graph I compare on day 151 (31st May) of each year the area per thickness categories. Here I sum the bins, starting with the highest thickness to get lines indicating ice thicker than 16.24, thicker than 12.39 all the way to ice thicker than 0 .

Now the line indicating thicker than 1.46m (fourth from the top) is kind of interesting. The 1.46m is close to what (in the PIOMAS universe) can be melted down to zero within a single melting season. This is shown by plotting the 10th September area (bin area of all bins except the first) (dash-dotted line) which is near the ">1.46 31st May" line, bit above before 2007, below after that.

The "volume gap" is clearly visible and suggests a possible record low area. Note that the 2012 record low is not "foreseen", that could happen again (in the opposite direction).

Anyway with the data that I have I may be able to do something of interest....Now the line indicating thicker than 1.46m (fourth from the top) is kind of interesting. The 1.46m is close to what (in the PIOMAS universe) can be melted down to zero within a single melting season. This is shown by plotting the 10th September area (bin area of all bins except the first) (dash-dotted line) which is near the ">1.46 31st May" line, bit above before 2007, below after that.

The "volume gap" is clearly visible and suggests a possible record low area. Note that the 2012 record low is not "foreseen", that could happen again (in the opposite direction).

Something of interest indeed! What a great graph. As has been said many times - and is shown here perfectly - extent and area don't tell the whole story.There are some factors like the regional distribution of the thick ice, and the uncertainties and possible errors of PIOMAS, not to mention the weather, but 2017's chances of some kind of record in September are indeed significant when looking at that >1.46 line.

Fascinating, Wipneus!I get the impression that some folks are asking for information like this, only for just the CAB (my preference) or for the several open-ocean Arctic basins (as a unit). I would hazard to guess the CAB only data would show the May 31st 1.46m line crossing the September 10th line about next year (that is, it doesn't cross yet, but is getting close). (Even this year, the CAB was mostly thicker than 1.46m on May 31.)

When comparing the ">1.46m" curve with the "Area 10 September" curve, it is striking how the latter curve is above the former for every single year before 2007, below for 2007 and every single year afterwards.

It's perhaps the most convincing illustration I have seen showing 2007 as a tipping point year.

Is it because 2007 wiped out a lot of older ice, resulting in younger ice age distributions in the years after?

Or was a tipping point reached in area? The ice could move around more within the Arctic basin. Longer fetches became available for waves to develop and crash into the edges of the pack? More moisture arising from open water? More wind due to the open water?

Or some combination of the above?

In any case, there appears to be a genuine discontinuity between the years up to 2006 and those from 2007 onwards. At the very least, there is a strong trend for the "10 September area" curve progressively dropping to below the ">1.46m" curve. Thicker ice is now melting out by September than used to be the case in the earlier years. I don't think it can be palmed off as a statistical variation.

Fascinating indeed. Not sure however that the bucket distribution is terribly appropriate to the post-2k regime! Right now it seems that almost all of the ice about which there is any uncertainty as to prospects for the summer is lumped into a single bucket. (i.e. 1.46m < thickness <2.61m) At the same time, ice over 9m thick, which is essentially extinct, has four buckets all to itself.